Method for automatically locating a motor vehicle wheel and corresponding locating unit

ABSTRACT

A method for automatically locating a motor vehicle wheel comprises the following steps: transmission by the wheel unit ( 12   a  to  12   d ) of high-frequency signals representing, at least, the wheel pressure whereon the wheel unit is mounted, and a code identifying the wheel; reception by the central unit ( 11 ) of the high-frequency signals transmitted by the wheel unit. The method further comprises the following steps: transmission of low-frequency signals by at least a transmission device ( 14, 14 ′) mounted on the vehicle proximate to the wheels along a predetermined position, so as to activate the units arranged proximate; reception of the low-frequency signals by the wheel units and in response, transmission of high-frequency signals by the activated wheels, the signal comprising at least the code identifying the activated wheels, and reception of the high-frequency signal by the central unit ( 11 ) associated with the code identifying the activated wheels, at the position of the transmission device(s)  14, 14 ′).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the 35 USC 371 national stage of internationalapplication PCT/EP01/14174 filed on 4 Dec. 2001, which designated theUnited States of America.

The present invention relates to a process for automatically locatingthe wheels of a motor vehicle and a corresponding locating unit.

BACKGROUND OF THE INVENTION

It is already known to measure and to monitor the pressure inside thetires of each of the wheels of a vehicle. The pressure thus measured(and/or other parameters) is conveyed by a high-frequency signal to acentral computation unit situated in the vehicle. This central unit hasthe function of processing the signals received and of informing thedriver as to any abnormal pressure of the tires (or abnormal rise intemperature, etc). In general this central computation unit is disposedin the passenger compartment of the vehicle and manages all thefunctions implemented in this passenger compartment. In order for thiscentral computation unit to correctly process the signals received, itis imperative that it can unambiguously determine the origin thereof.

For this purpose, processes (so-called locating processes) exist whichmake it possible to determine where the wheel transmitting a signal issituated, but these processes are either lengthy, or onerous, or complexand often require considerable computation times before managing toassign a precise transmission site on the vehicle (for example, frontright, front left, rear right or rear left) to each signal received.

SUMMARY OF THE INVENTION

The aim of the present invention is to rapidly locate the wheels of amotor vehicle. The process according to the invention must furthermorebe automatic, reliable and cheap. Preferably, one seeks to reduce thecost of this locating function by using the fewest possible specificcomponents.

For this purpose the present invention relates to a process forautomatically locating the wheels of a motor vehicle, said vehiclecomprising a wheel unit integral with each of the wheels of the vehicleand a central computation unit disposed in the vehicle, said processcomprising the following steps:

-   -   transmission by the wheel unit of high-frequency signals        representative, at least, of the pressure of the wheel on which        the wheel unit is mounted, as well as of a code identifying this        wheel,    -   reception by the central unit of the high-frequency signals        transmitted by the wheel unit,        said process being characterized in that it furthermore        comprises the following steps:    -   transmission of a low-frequency signal by at least one        transmission device mounted on the vehicle in proximity to the        wheels according to a predetermined position, in such a way as        to wake up the wheel units placed in proximity,    -   reception of this low-frequency signal by the wheel units and,        in response, transmission of a high-frequency signal by the        woken-up wheels, said signal comprising at least the code        identifying the woken-up wheels, and    -   reception of the high-frequency signal by the central unit and        association of the code identifying the woken-up wheel units,        with the position of the transmission device.

Thus, by placing the low-frequency transmission device in proximity tothe wheels of one and the same axle (for example), it is certain thatonly the wheels of this axle will respond to the low-frequency signaltransmitted by the transmitter. This is because a low-frequency signalcan be picked up only within a limited radius of action (for example 1m).

Advantageously the transmission of the low-frequency signal is performedby antennas disposed in the handles, side trims, rear-view mirrors, etcand used in addition by a device for remote control of access on boardthe vehicle.

Thus it is the antennas which already serve for the locking/unlocking ofthe vehicle which are re-used here to wake up the electronic wheelunits. By using antennas which already exist on most vehicles, the costof the process according to the invention is reduced.

Of course when the vehicle is not already equipped with such antennas,it suffices to place three low-frequency transmission devices in frontof three wheels of the vehicle so as to automatically pinpoint thesethree wheels. The last wheel position is deduced from the threepositions found.

More advantageously, when the transmitting antennas (transmissiondevice) placed in the handles are used (these antennas already servingfor the control of locking/unlocking of the openable panels), thelow-frequency signal sent to the wheel units is an uncoded signal, whilewhen these antennas are used in their vehicle locking/unlockingfunction, they use a coded low-frequency signal. Thus, to locate thewheels, it is sufficient to remove the coding. Here again a substantialsaving is made.

The present invention also relates to a unit for locating the wheels ofa motor vehicle implementing the process described hereinabove.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, characteristics and advantages of the present inventionwill emerge moreover from the following description, by way ofnonlimiting example and with reference to the appended drawings inwhich:

FIG. 1 is a diagrammatic view of a motor vehicle fitted with a locatingunit according to the invention,

FIG. 2 is a view similar to FIG. 1 showing a variant embodiment of thelocating unit according to the invention, and

FIG. 3 is a diagrammatic view showing the locating unit according toFIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

According to the embodiment shown in FIGS. 1 and 3, the locating unit 10according to the invention comprises:

-   -   a central computation unit 11, placed in a vehicle 13,    -   a plurality of wheel units 12 a to 12 d each integral with one        of the wheels 15 of the vehicle, and    -   a transmission device 14 integral with the vehicle and placed        according to a known position on this vehicle. For example, in        proximity to the wheels of one and the same axle (E₂ in FIG. 3).

The central computation unit 11 is an electronic computer managing forexample all the functions required in the passenger compartment of avehicle. In a known manner, such a computer is customarily placed underthe dashboard (but this is not limiting). This computer is fitted with areceiving antenna suitable for receiving high-frequency signalstypically in the 315 MHz or 433 MHz region. Such signals exhibit theparticular feature of having a very large range (for example 10 m) butdo not transport energy. These signals are commonly used for theopening/closing of the openable panels at large distance, the telephoneor the alarm.

The wheel units 12 a to 12 d are all similar and comprise a pressuresensor of known type (not detailed here) and an RF (radio frequency)device 16 for transmitting the measured data. The latter are transmittedto the central unit 11 regularly and/or when a specified event sonecessitates. Other parameters may also be transmitted to the centralunit, for example the temperature of the tire, its acceleration etc.Together with this set of parameters the wheel unit also transmits anidentifying code specific to it. This set of data is transmitted to thecentral unit 11 by a high-frequency signal.

According to the invention, to determine the identifying code of eachwheel, a transmission device 14 placed on the vehicle is used. In theexample illustrated, this device is placed in proximity to a specifiedaxle.

In the example represented in FIGS. 1 and 3 this transmission device ismade up of antennas 14, of known type, placed in the rear doors of thevehicle so as to allow their remote locking/unlocking. On instructionfrom the central unit 11, these antennas transmit a low-frequency signal(typically of the order of 125 kHz). Such a signal exhibits theparticular feature of having a low range (1 m), and can transportenergy. It can therefore allow the waking-up of a transponder situatedin the wheel unit.

When these antennas are used to locate a wheel, they transmit an uncodedsinusoidal low-frequency signal.

Thus even if this signal is picked up by the remote locking/unlockingdevice, it is not understood and causes no untimely opening of thevehicle. On the other hand this uncoded signal is received by thetransponder of the wheel units situated in the zone of action of thisantenna (in the present case, the rear wheels). Advantageously, by usingthe antennas of the rear doors of the vehicle only the wheel unitssituated on the rear axle E₂ of the vehicle can pick up this signal. Thewheel units placed on the wheels of the front axle E₁ are too far away(range limited to 1 m) and do not receive this low-frequency signal.

It will be noted, as a variant, that even if the antennas 14 of thefront wheels of the vehicle transmit a low-frequency signal at the sametime as the rear antennas, only the rear wheels will receive thissignal. This is because the customary configuration of a vehicle is suchthat in general the antennas of the handles of the front wheels arecloser to the rear wheels than to the front wheels.

When the wheel units of the rear axle receive this low-frequency signal,they wake up (transponder) and send their data and their identifyingcode to the central unit. Hence, the central unit 11 receives twoidentifying codes. Since it is the central unit 11 which prompted thetransmission of the low-frequency signals by the antennas of the reardoors, it immediately associates these identifying codes with the rearwheels of the vehicle. By deduction the central unit attributes theother identifying codes that it receives to the front wheels of thevehicle.

For safety reasons one waits for the central unit to have attributed thesame identifying codes to the same wheels several times in succession inorder to regard the identification as reliable and definitive. Duringthe remainder of the journey of the vehicle, the identification of theposition of the wheels is then no longer performed.

It will be noted that according to the invention the association of awheel unit identifying code with a position on the vehicle is carriedout with the aid of antennas already installed on the vehicle (for someother purpose entirely). The benefit of the present invention residesessentially in the fact that this association (identifyingcode/position) is performed without adding any extra element to thevehicle. Moreover this association is fast, reliable and inexpensive.

As a variant (FIG. 2) it is possible, when the vehicle is not alreadyequipped with antennas in its doors to mount specific antennas 14′ inproximity to the wheels of one and the same axle (front axle E₁, forexample, in the example represented in FIG. 2). In this case the wheelswhich send their identifying code following the activation of theantennas 14′ are the front wheels. The central unit attributes the othertwo identifying codes to the rear wheels.

Of course by using a process (not described here) for locating the rightand left wheels, it is then possible to completely individualize the setof wheels of a vehicle and the corresponding identifying codes.

As a variant (not represented) it is possible by using threetransmission devices (specific or otherwise) to prompt the response ofeach of the wheel units separately. The central unit activating each ofthe wheel antennas one by one receives the responses from the wheelunits one by one. Hence, the central unit is able to associate anidentifying code with a single position of a wheel of the vehicle. Thefourth position is deduced. When this process has been implementedseveral times and the results are stable, the central unit regards theidentification of the codes to have been acquired.

The locating process according to the invention comprises the followingsteps:

-   -   transmission by the wheel unit 12 a to 12 d of high-frequency        signals representative, at least, of the pressure of the wheel        15 on which the wheel unit is mounted, as well as of a code        identifying this wheel,    -   reception by the central unit 11 of the high-frequency signals        transmitted by the wheel unit 12 a to 12 d,        said process being characterized in that it furthermore        comprises the following steps:    -   transmission of a low-frequency signal by at least one        transmission device 14, 14′ mounted on the vehicle according to        a predetermined position, in such a way as to wake up the wheel        units 12 placed in proximity,    -   reception of this low-frequency signal by the wheel units 12 a        to 12 d and, in response, transmission of a high-frequency        signal by the woken-up wheels, said signal comprising at least        the code identifying the woken-up wheels, and    -   reception of the high-frequency signal by the central unit 11        and association of the code identifying the woken-up wheel        units, with the position of the transmission device or devices.

Of course, the present invention is not limited to the embodimentsdescribed hereinabove. Thus, it is possible to determine the position ofthe wheels situated on one of the sides of the vehicle by placing theantennas 14, 14′ on that side alone.

1. A process for automatically locating the wheels of a motor vehicle, said vehicle comprising a wheel unit integral with each of the wheels of the vehicle and a central computation unit disposed in the vehicle; said process comprising the following steps: transmitting by the wheel unit high-frequency signals representative, at least, of the pressure of the wheel on which the wheel unit is mounted, and a code identifying the wheel; receiving by the central computation unit the high-frequency signals transmitted by the wheel unit; transmitting an uncoded low-frequency signal by at least one transmission device comprising antennas disposed in the doors of the vehicle and used in addition, by a device for remotely locking/unlocking said doors; said transmission device being mounted on the vehicle in proximity to the wheels according to a predetermined position, in such a way as to wake up the wheel units placed in proximity; receiving said uncoded low-frequency signal by the wheel units, and in response thereto, transmitting a high-frequency signal by the woken-up wheels; said high-frequency signal comprising at least the code identifying the woken-up wheels; and receiving the high-frequency signal by the central unit, and associating the code identifying the woken-up wheel units, with the position of the transmission device or devices.
 2. The process as claimed in claim 1, wherein said transmission device also comprises specific antennas disposed in proximity to the wheels of the vehicle.
 3. The process as claimed in claim 1, wherein said transmission device comprises specific antennas disposed in proximity to the wheels of the same axle.
 4. A locating unit for implementing the process as claimed in claim 1, said locating unit comprising: a central computation unit placed in the vehicle; a wheel unit integral with each of the wheels and at least one transmission device; said transmission device being structured and arranged to transmit a low-frequency signal; said transmission device comprising an antenna placed in each door of the motor vehicle; said antennas also being adapted to communicate with a device for remotely locking/unlocking the doors of the vehicle. 